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Work Functions and Injection Barriers
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
The KP is a simple measurement operationally, but it has the disadvantage of poor spatial resolution. The plate electrodes have sizes of the order of mm, and therefore they provide an average of the surface properties. To obtain a high resolution of the CPD at the nanometer scale, one may attempt to reduce the size of the capacitor plate using a tip of atomic force microscopy (AFM). However, this procedure usually results in poor resolution due to small currents. The technique of Kelvin Probe Force Microscopy (KPFM) successfully determines the CPD between a conducting tip of AFM tip and a sample by measuring the electrostatic force. Note that in KPFM the voltage measured is the difference between the VL at the sample surface and the VL at the surface of the tip, ΔψCPD=ψsampleeq−ψrefeq.
Probing Dielectric Constant at the Nanoscale with Scanning Probe Microscopy
Published in Jian V. Li, Giorgio Ferrari, Capacitance Spectroscopy of Semiconductors, 2018
Laura Fumagalli, Gabriel Gomila
With the invention of SPM in the 1980s, many scanning probes microscopes have been developed to access electrical properties of solids and liquids at the nanoscale simultaneously to structural properties [1, 2]. The first and simplest one is the scanning tunnelling microscope (STM), probing the tunnelling current through an atomically sharp asperity of a metallic wire with atomic spatial resolution. However, STM has a number of limitations, e.g. the electrical image is coupled to the surface topography and limited to conductive samples or to insulating samples as thin as few atomic layers. To overcome these limitations, several electrical techniques based on the AFM have been introduced in the late 1980s, probing local electrical properties with a small sharp tip mounted on a cantilever. They are advantageous because the electrical information is decoupled from topography. Furthermore, they can be applied to virtually any type of samples (metallic and insulating) by combining different sensing technologies (electrical, mechanical and optical). Therefore, electrical AFM techniques such as conductive-AFM, scanning capacitance microscopy (SCM), electrostatic force microscopy (EFM) and Kelvin Probe Force microscopy (KPFM), which probe impedance (capacitance), electrostatic force and contact potential, respectively, have rapidly gained popularity [2].
Substrate-morphology driven tunable nanoscale artificial synapse
Published in Journal of Asian Ceramic Societies, 2021
Shahid Iqbal, Mohit Kumar, Ranveer Singh, Qadeer Akbar Sial, Hyungtak Seo
To investigate a nanoscale charge transport, conductive atomic force microscopy (c-AFM) has been used, which is used to obtain an evidence about the topographic changes and simultaneously local electrical conduction at nanoscale [25–27]. Conductive tip used in c-AFM as a top electrode offer the possibility to the precise location of the device even at 10-nm level, which is useful in scaled-down semiconductor devices [28]. Meanwhile, this kind of nanoscale engineering gives a way toward the critical applications of modernized concepts of artificial neuromorphic computing. Recently, such nanoscale synaptic devices have been implemented in advanced neuromorphic applications [15,29]. Normally, surface-treated substrate at different level causes difference in work function of the device [30]. Furthermore, Kelvin probe force microscopy (KPFM) is a non-contact mode that offers the measurement of potential difference between its conduction tip and device surface at high spatial resolution as well as calculate the carrier concentration [31].
Evolution of millimetric-range electrostatic forces between an AFM cantilever and a charged dielectric via suspended force curves
Published in The Journal of Adhesion, 2022
Tianmao Lai, Mingli Guo, Yuguo Chen
Atomic force microscope (AFM) is a versatile equipment for surface force measurements with very high accuracy, both vertically and laterally.[1] When the dominant force is a long-range electrostatic force, the technique is always regarded as electrostatic force microscopy (EFM). As a dynamic non-contact mode, EFM has been widely used in measure surface charges,[2,3] surface potentials[4] and electric properties.[5,6] With some modifications, an AFM can be used as a Kelvin probe force microscopy (KPFM), which is powerful to measure surface potentials and work function.[7]